The difficulty with the synthesis of perfluoro esters lies in instability of the ester linkage toward hydrogen fluoride and the facile dissociation of perfluoro esters by nucleophilic attack. The electrolytic fluorination of esters is precluded because they are spontaneously decomposed in the acidic solution. The direct fluorination of ethyl acetate (See Adcock, J. L. et al., J. Org. Chem. 40, 3271 (1975)) represents the first successful fluorination of an ester, giving CF.sub.3 COOCF.sub.2 CF.sub.3 and CF.sub.3 COOCHFCF.sub.3 in 5% and 20% yield respectively. Extension of this direct fluorination technique has previously led to the conversion of hydrocarbon polyesters to highly fluorinated polyesters, which are important precursors to perfluoropolyethers. Persico, D. F. et al., J. Am. Chem. Soc. 107, 1197 (1985).
There were few reports of the preparation of perfluoroesters by indirect methods. The first reported reactions were the dimerization and trimerization of COF.sub.2 to yield FCO.sub.2 CF.sub.3 and (CF.sub.3 O).sub.2 CO respectively. Photolysis reaction of CF.sub.3 OF and CF.sub.3 OOCF.sub.3 in the presence of CO resulted in the same products as above reactions. Aymonino, P. J., Chem. Commun. 241 (1965); Varetti, E. L. and Aymonino, P. J., Chem. Commun. 680 (1967). A more general synthesis is the low temperature reaction of perfluoroacyl fluorides with perfluoro alkoxide salts.
With the execption of the reaction of fluoroesters R.sub.f COOCH.sub.3 with dimethyl sulfone to yield ortho esters R.sub.f C(OCH.sub.3).sub.3 (Holm, T., U.S. Pat. No. 2,611,787 (1952)) and the isolation of CHFClC(OC.sub.2 H.sub.5).sub.3 by Tarrant and Brown (Tarrant, P. and Brown, H. A., J. Am. Chem. Soc. 73, 1781 (1951)) little synthetic information on fluorinated ortho esters has appeared in the literature.